New Physician-Investigators Receiving
National Institutes of Health
Research Project Grants
A Historical Perspective on the “Endangered Species”
Howard B. Dickler, MD Di Fang, PhD
Stephen J. Heinig, MA Elizabeth Johnson, MS David Korn, MD
D
ECLINES IN THE NUMBER OFphysician-scientist appli-cants and recipients of Na-tional Institutes of Health (NIH) research and training awards in the 1970s generated concerns that phy-sician clinical investigators would be-come an “endangered species” if trends continued unaltered.1In succeeding
de-cades, as unprecedented scientific and technological progress in biomedicine and related disciplines moved discov-eries ever closer to clinical relevance, concerns continued about the ad-equacy of the physician-scientist work-force. Consistently expressed con-cerns include changing market forces adversely affecting the environment for clinical scholarship in medical schools and teaching hospitals, and clinical re-search faring less well than laboratory research in the NIH’s well-established review and award processes for grants. Since the 1970s, eminent panels and authors have examined the plight of phy-sician-scientists and clinical investiga-tors,2-5and several have influenced policy
and programmatic interventions. The most influential examination has been the Nathan Committee report that sparked creation of new NIH training and career development programs for
patient-oriented researchers, and led Congress to authorize several new edu-cational loan repayment programs for clinical researchers.6In 2003, the NIH
launched its Roadmap initiatives, which include a focus on “re-engineering the clinical research enterprise”7and
des-Author Affiliations: Division of Biomedical and Health Sciences Research, Association of American Medical Colleges, Washington, DC (Drs Dickler and Korn and Mr Heinig); American Association of Colleges of Nurs-ing, Washington, DC (Dr Fang); and Department of Biostatistics, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Md (Ms Johnson). Corresponding Author: David Korn, MD, Associa-tion of American Medical Colleges, 2450 N St NW, Washington, DC 20037 ([email protected]). Context Although concerns have persisted for decades about the production of new
physician clinical scientists and their success in receiving and sustaining research sup-ported by the National Institutes of Health (NIH), no comprehensive analysis docu-ments the experiences of first-time investigators with an MD over a long period.
Objective To ascertain the perseverance and comparative success of
physician-scientists competing for NIH research (R01) grants awarded over 40 years.
Design, Setting, and Participants A longitudinal, comparative study of all
first-time applicants and recipients of NIH R01 grants between 1964 and 2004 stratified by the principal investigators’ major degrees (MD, PhD, or MD and PhD) and their proposed involvement in research of humans or human tissues.
Main Outcome Measures Number of first- and second-time NIH R01 grant
appli-cants and recipients by academic degree and by research type (clinical vs nonclinical).
Results The annual number of first-time investigators with an MD only as NIH R01
grant applicants remained remarkably stable over 4 decades (41-year mean of 707 [range, 537-983] applicants). Among first-time applicants, those with an MD consis-tently had less success in obtaining funding (mean annual percentage [MAP], 28%) than either investigators with a PhD (MAP, 31%; P=.03 vs MD only) or both an MD and a PhD (MAP, 34%; P⬍.001 vs MD only and P=.002 vs PhD only). Among in-vestigators who obtained a first R01 grant, those with an MD were consistently less likely (MAP, 70%) than those with a PhD (MAP, 73%; P=.04 vs MD only) or those with an MD and a PhD (MAP, 78%; P⬍.001 vs MD only and P=.007 vs PhD only) to obtain a subsequent R01 grant. First-time applicants with an MD were much more likely to propose clinical research (MAP, 67%) than applicants with an MD and a PhD (MAP, 43%) and applicants with a PhD only (39%). First-time applicants with an MD only who proposed clinical research were funded at lower rates than their MD-only counterparts proposing nonclinical research (23% vs 29%, respectively; P⬍.001).
Conclusions From 1964-2004, the number of physician-investigators applying for
first R01 grants showed little net change. Physician-investigators consistently experi-enced higher rates of attrition and failure, even after receiving a first R01 grant, and those proposing clinical research were less successful in obtaining funding than phy-sicians proposing nonclinical research.
ignate major resources to clinical re-search training, career development, and shared resources. In 2005, the NIH launched a bold Clinical and Transla-tional Sciences Award program cen-tered on creating academic homes for clinical research in universities and teaching hospitals.8
Concerns about the status of clini-cal investigation persist and are now ex-acerbated by the current NIH budget and the prospect of an indeterminate period of flat or diminishing purchas-ing power by the NIH. In this circum-stance, new initiatives become more dif-ficult to sustain both materially and politically.9Challenging policy and
re-source allocation decisions loom both for the NIH and the academic medical community.10
This study was undertaken with a conviction that a common and accu-rate perception of the experience of physician-scientists awarded NIH re-search grants during the past 40 years could help dispel misunderstanding and inform sounder policy making. Both the health of the environment for physi-cians conducting hypothesis-generat-ing clinical research and the caliber of their science are reflected in the pool of new physician applicants for NIH tra-ditional research awards and their sub-sequent success. Accordingly, the fol-lowing were compared from the earliest available years: the annual numbers of first-time applicants with an MD, a PhD, and an MD and a PhD for traditional NIH research project grants; the rela-tive likelihood of receiving the first grant awards; the likelihood of their ap-plying for and receiving a subsequent NIH award whether successful or not in receiving a first grant; and the fates of these applicants according to whether their grant applications and awards were coded as clinical by the NIH.
METHODS
Data from NIH’s Consolidated Grant Applicant File between 1964 and 2004 were analyzed for trends in the annual number of first-time applicants for NIH R01 grants. The analysis was com-pleted in 2006.
The R01 is the US Public Health Ser-vice’s administrative code designating “[traditional] research grants.” As de-fined by the NIH, “the Research Project (R01) grant is an award made to sup-port a discrete, specified, circum-scribed project to be performed by the named investigator(s) in an area rep-resenting the investigator’s specific in-terest and competencies, based on the mission of the NIH.”11
First-time applicants were individu-als who applied for no previous R01 grant, although they may have ap-plied for or received another type of NIH award. Common first awards in-cluded R23 or R29 first investigator awards but the latter have been discon-tinued. Application records for these first-time applicants were then matched by applicants’ unique identification numbers to determine whether they subsequently received a first R01 grant either on their original submission or any subsequent revision. Those who re-ceived funding for any amendment of that first R01 grant application were counted as successful on their first application.
This same cohort was subsequently analyzed, stratified by success or fail-ure for their first R01 grant applica-tion. Analysis was performed for those who failed to have their first R01 grant funded on their first or revised at-tempts but later applied for a different R01 grant, and principal investigators who received their first R01 grant and later applied for either a competing re-newal or second R01 grant. Each ap-plication in every analysis was counted only once no matter how many times revised and resubmitted. If any ver-sion was funded, that application was considered successful.
Applications and awards were cat-egorized as clinical research if investi-gators had checked a box in the grant application that indicated the pro-posed project involved humans or hu-man tissues, unless exemption 4 (in-volving use of deidentified data or specimens) was checked. This proxy is used by the NIH even though it over-estimates the volume of “true” clinical
research as defined by many.12
Con-tamination of clinical with nonclini-cal application data in this study would tend to minimize any differences ob-served, so significant differences be-come even more meaningful. Thus, for the purposes of this study, the proxy is explicit, objective, and instructive.
Regression models with autocorre-lated error terms were used to deter-mine the significance of differences in the mean outcomes across the differ-ent degree cohorts and across clinical vs nonclinical applications. These mod-els take into account the correlation in the data over time. The models as-sumed an autoregressive lag 1 correla-tion model, which implies an exponen-tially decaying correlation structure as the number of years between measure-ments increase. Three comparisons were made for each outcome (gators with an MD vs a PhD, investi-gators with an MD vs an MD and a PhD, investigators with a PhD vs an MD and a PhD).
To account for multiple compari-sons, the P values were adjusted using the conservative Bonferroni correc-tion (each P value was multiplied by 3). Significance was set at a level of .05. All statistical analyses were completed using SAS software version 9.1 (SAS In-stitute Inc, Cary, NC).
The presence in the Consolidated Grant Applicant File of both an MD and a PhD on an applicant record may in-dicate a graduate of a dual-degree pro-gram such as the NIH Medical Scien-tist Training Program. Other types of professional health degrees (eg, den-tistry, nursing, veterinary medicine, etc, which together comprise a small per-centage of Consolidated Grant Appli-cant File records) have been excluded for clarity of presentation.
RESULTS
First-Time Applicants
The number of investigators with an MD who annually apply for their first R01 grant has remained remarkably stable for the last 30 years (FIGURE1).
The steady decline in applicants with an MD during the late 1960s (from a
high of 983 in 1966 to a low of 537 in 1970) sparked concern by Wyn-gaarden1but the curve bottomed out
and subsequently recovered mod-estly. In the last year analyzed (2004), there were 689 first-time applicants with an MD, close to the 41-year mean of 707 (range, 537-983) applicants. In contrast, the numbers of first-time ap-plicants with an MD and a PhD in-creased during this period from 79 in 1964 to 511 in 2004, well above the 41-year mean of 157 (range, 50-511) ap-plicants, while first-time applicants with a PhD increased from 1423 in 1964 to 2869 in 2004, also above the 41-year mean of 2068 (range, 1423-3066) ap-plicants. Even if one considers physi-cian-scientists as a single group (inves-tigators with an MD plus inves(inves-tigators with an MD and a PhD), the net in-crease in first-time applicants from 1964 to 2004 was only 188 (1200−1012) ap-plicants, and that occurred primarily in the last several years.
Even during the doubling of the NIH budget between 1998 and 2003, the numbers of first-time applicants with an MD were largely unchanged (an ap-parent 4% decline was restored by 2004; Figure 1), while the numbers of first-time applicants with a PhD increased by more than 43% and applicants with an MD and a PhD increased by more than 104%.
Although the percentage of appli-cants with an MD whose first-time R01
grant applications are funded has var-ied over time, it has on average been lower than that of first-time appli-cants with a PhD (Figure 1). The mean annual percentage of first-time appli-cants with an MD who were awarded grants was 28%, while that for appli-cants with a PhD was 31% (P = .03 vs MD only) and for applicants with an MD and a PhD was 34% (P⬍.001 vs MD only and P = .002 vs PhD only). Applicants for Second R01 Grants When those first-time applicants who had received funding for a first R01 grant apply for a second R01 grant (FIGURE2), a lower percentage of
ap-plicants with an MD only receive fund-ing (mean annual percentage of 70%) than applicants with a PhD (mean an-nual percentage of 73%; P = .04 vs MD only) and applicants with an MD and a PhD (mean annual percentage of 78%;
P⬍.001 vs MD only and P=.007 vs PhD
only). To examine the differences seen in the funding of applicants for a sec-ond R01 grant, separate analyses were performed to determine whether the differences were due to the rate of re-application or due to the success rate of those who reapplied. The differ-ence between second applicants with an MD and those with a PhD was largely due to a difference in the rate of reap-plication (P = .005) and not in the suc-cess rate of those who reapplied (P=.17). For applicants with an MD and
a PhD compared with an MD only, there were significant differences in both re-application rates (P = .001) and suc-cess of those who reapplied (P⬍.001). The same was true for applicants with an MD and a PhD compared with those with a PhD only (P = .02 for reapplica-tion and P=.04 for success of those who reapply). For all 3 cohorts, the percent-age of successful first-time applicants who subsequently received another R01 grant increased over time.
Unsuccessful First-Time Applicants For individuals who failed to obtain funding for their first R01 grant appli-cation but who later applied for a dif-ferent R01 grant (Figure 2), the data again show that a lower percentage of individuals with an MD only (23%) are funded than those with a PhD only (25%; P⬍.001 vs MD only), who are in turn lower than those with an MD and a PhD (34%; P⬍.001 vs those with either an MD or a PhD). Separate analy-ses showed that the difference in ob-taining funding between individuals with an MD and those with a PhD was due to a difference in the reapplica-tion rate (P⬍.001) and not a differ-ence in the success rate among those who reapplied (P⬎.99). For those with an MD and PhD vs either those with an MD or those with a PhD, there were sig-nificant differences in rates of both re-application and success among those who reapply (P⬍.001 for all compari-sons).
Clinical vs Nonclinical Research Using coding for humans and human tissues as a surrogate marker, the data confirm intuition that physicians are more likely than nonphysicians to pur-sue clinical research. A mean of 67% of individuals with an MD who apply an-nually for a first R01 grant application pursue clinical research. The percent-age is much lower for physicians who also have a PhD (43%) and for inves-tigators with a PhD only (39%). Nev-ertheless, because of their greater num-bers, more investigators with a PhD submit clinical applications (mean of 60% of applicants proposing clinical
re-Figure 1. First-Time Applicants for R01 Grants by Degree (1964-2004) and Percentage
Awarded (1964-2003) 3000 1000 1500 2000 2500 500 0 1964 1972 1980 1988 1996 2004 1964 1972 1980 1988 1996 2004 First-Time Applicant Cohort Year
Count
First-Time Applicants for R01 Grants Percentage Awarded
MD PhD MD and PhD 60 20 30 40 50 10 0
First-Time Applicant Cohort Year
Per
centage
search for all years) than those with an MD and those with both an MD and PhD (40%). This ratio was steady over the 21 years analyzed. The total num-ber of applicants whose grants were coded as clinical has averaged 1385 for the 21 years and has risen gradually during that period (from 1311 in 1984 to 1843 in 2004).
FIGURE3 shows that the annual
per-centage of applications by individuals with an MD who are funded for their first R01 grant is on average lower for those who conduct clinical research than those who conduct nonclinical re-search (23% vs 29%; P⬍.001). While individuals with an MD and a PhD were more successful than those with an MD only overall, a similar difference in ob-taining funding between those perform-ing clinical and nonclinical research was observed (28% vs 35%; P⬍.001).
When first-time applicants who had received their first R01 grant applied for a second R01 grant, the difference in obtaining funding between clinical and nonclinical research was again substan-tial: 72% vs 80% (P = .02) for individu-als with an MD and 76% vs 86% (P = .003) for individuals with an MD and a PhD (Figure 3). The designa-tion of clinical refers to the first appli-cation. Separate analyses of these dif-ferences indicated that for individuals with an MD, the difference was due to a lower rate of reapplication (P⬍.001) but not a difference in the success rate of those who reapply (P = .34). For in-dividuals with an MD and a PhD the op-posite was true, with the difference being due to a lower success rate among those clinical investigators who reap-ply (P = .005) but not to a difference in the rate of reapplication (P = .68).
Among individuals whose applica-tions for a first R01 grant were unsuc-cessful but who later applied for a dif-ferent R01 grant, the mean annual percentages of grant recipients were again lower for clinical than nonclini-cal research (20% vs 27%, P⬍.001 for those with an MD only; 31% vs 37% for those with an MD and a PhD, P = .45), but for the latter the difference was not significant. The designation of clinical
refers to the first application. The dif-ference for those with an MD only was due both to lower rates of reapplica-tion (P⬍.001) and lower percentages of reapplicants being funded (P = .04). Finally, how consistently first-time applicants for R01 grants in clinical re-search pursue clinical rere-search in sub-sequent R01 grant applications was ex-amined. A strong concordance was found; for example, about 80% of first-time recipients of clinical R01 grants with an MD who apply for a second R01 grant persist with clinical research. A similar concordance exists for nonphy-sicians and for first-time unsuccessful applicants who reapply for R01 grants.
COMMENT
By focusing exclusively on first-time R01 grant applicants and their subsequent success, this analysis has several strengths. It measures specific cohorts of individuals, not the number of appli-cations alone, which is influenced by in-dividuals submitting multiple applica-tions. It examines trends across several decades and thereby avoids focusing on trends during narrow time intervals, which can be aberrant and suggest mis-leading conclusions.13Given the wide
variation across the types of projects and
awards funded by the NIH, the R01 grants are universally recognized as em-bodying competitive, meritorious, hy-pothesis-testing research as discerned by peers, and nearly half (44% in 2004) of the NIH extramural budget supports R01 grants.
Our analysis does not distinguish be-tween R01 grants that were investigator-initiated or invited by specific requests for applications or program announce-ments, although the vast majority of R01 grants are initiated by the investigator. Although certainly not the sole mea-sure of productive research, receipt of an R01 grant has come to be considered a threshold event launching a career as an independent investigator and is often ac-corded great weight by institutional ap-pointments and promotions commit-tees. Similarly, the clinical research community recognizes the volume of R01 grant support for clinical investiga-tion as a reliable, measurable signal of the status and vitality of the discipline.4
Despite remarkable scientific and funding opportunity, the pool of avail-able physician-investigators has not in-creased for many decades. Although physician-investigators do not appear in danger of extinction from the R01 grant pool, the growth of this cohort has
Figure 2. First-Time Applicants Who Received A Second R01 Grant (1964-1998) and
First-Time Unsuccessful Applicants Who Later Received an R01 Grant (1964-1998)
First-Time Successful Applicants Who Received Another R01 Grant
First-Time Unsuccessful Applicants Who Reapplied and Received an R01 Grant 60 20 30 40 50 10 0 1964 1972 1980 1988 1996 First-Time Applicant Cohort Year
Per
centage
1964 1972 1980 1988 1996 First-Time Applicant Cohort Year 100 70 80 90 60 50 Per centage MD PhD MD and PhD
Data for years after 1998 are omitted because insufficient time has elapsed for recent recipients of first R01 grants (with an average length of 4.1 years) to maximize their opportunity to apply for a second award. The percentage range indicated on the y-axes differ between the 2 plots; the range in common is indicated in blue. For first-time successful applicants who received another R01 grant, P=.04 for MD vs PhD; P⬍.001 for MD vs MD and PhD; P=.007 for PhD vs MD and PhD. For first-time unsuccessful applicants who reapplied and re-ceived an R01 grant, P⬍.001 for all comparisons (MD vs PhD, MD vs MD and PhD, and PhD vs MD and PhD).
certainly been less than nonphysician-investigators. Following the decline in the middle 1960s, the numbers of new applicants have fluctuated within a re-markably steady band for the past 3 de-cades. Although the percentage of ap-plicants with an MD receiving an award decreased from the early 1960s to the early 1980s, it has generally not de-clined for the past 2 decades.
The lack of increase in the number of applicants with an MD only con-trasts with the increases seen in both applicants with a PhD and applicants with an MD and a PhD, and is discor-dant with a number of other relevant factors. First, the size of the pool was unresponsive to the approximate dou-bling in the number of allopathic medi-cal graduates during the 1970s or the increasing physician work force. Al-though the annual number of allo-pathic graduates stabilized between 1980 and 2004 at about 15 700 (15 632 in 1980; 15 736 in 2004), during this period there was a substantial in-crease in physicians with medical de-grees from non-US institutions,14
ad-mittedly driven almost exclusively by
the needs of the health care delivery sys-tem. Second, from 1983 to 2004, infla-tion-adjusted annual funding for NIH traditional research project grants in-creased by 148%, the funding per grant adjusted for inflation increased by 36%, the number of these grants increased by 76%,15the pace of scientific
discov-ery and its increasing applicability to human disease were unparalleled, and the medical research frontier truly seemed endless16—all of which might
have been expected to attract physi-cians into careers in science but did not. Notably, the applicant pool of individu-als with an MD did not grow signifi-cantly, even during the doubling of NIH funding.
First-time applicants with an MD only for an R01 grant are consistently less persistent and successful than ap-plicants with a PhD or apap-plicants with an MD and a PhD. Throughout the ex-amined interval, first-time applicants with an MD have consistently been less likely than applicants with a PhD or ap-plicants with an MD and a PhD to re-ceive an R01 grant, and less likely, if not funded, to eventually receive a
differ-ent R01 grant. Even when successful at obtaining a first R01 grant, investiga-tors with an MD are less likely to re-ceive a second R01 grant. Whether ap-plicants were successful or unsuccessful in receiving a first R01 grant, lower re-application rates were a major cause of their diminished likelihood of receiv-ing a subsequent R01 grant. Thus, at ev-ery point in the early life cycle of an R01 investigator—time applicant, first-time recipient applying for a second R01 grant, or first-time unsuccessful appli-cant applying for a different R01 grant—investigators with an MD only have generally been less successful than investigators with a PhD or investiga-tors with an MD and a PhD, and more likely to exit the cycle. The attrition rate for investigators with a PhD and inves-tigators with both an MD and a PhD is also high but has been offset by in-creases in first-time applicants. It is im-portant to underscore that we are ob-serving attrition from the NIH R01 grant pool but not necessarily from re-search; we have no information on the career choices made by those who leave the R01 grant pool.
Physician clinical researchers are more likely than nonclinical research-ers to leave the R01 grant applicant pool. Consistently during the study interval, physician-scientist (MD only or MD and PhD) R01 grant applicants were more successful when they proposed non-clinical projects, consistent with the find-ings of Kotchen et al17that clinical
re-search applications fare less well than nonclinical applications in the NIH re-view system. Kotchen et al have ob-served that the “bias” seems not to be explained by the composition of the study sections, lack of focus in the study section on clinical research topics, or other factors endemic to the system but rather can often be attributed to intrin-sic difficulties with the applications, of-ten involving procedural or administra-tive requirements in studying humans.18
Taken together, our results portray re-markably consistent patterns of com-parative success across more than 3 de-cades for physicians and nonphysicians who are first-time R01 grant
appli-Figure 3. First-Time Applicants and Receivers of R01 Grants by Research Type (1984-2003)
and First- and Second-Time Receivers of R01 Grants by Research Type (1984-1998)
MD Clinical Research Nonclinical Research MD and PhD Clinical Research Nonclinical Research 60 20 30 40 50 10 1996 2000 1988 1992 1984
First-Time Applicant Cohort Year
Per
centage
First-Time Applicants and Receivers of R01 Grants
by Clinical Research Type
100 70 80 90 50 1996 1988 1992 1984
First-Time Applicant Cohort Year
Per
centage
First- and Second-Time Receivers of R01 Grants by Clinical Research Type
60
0
Data for years after 1998 are omitted because insufficient time has elapsed for recent recipients of first R01s to maximize their opportunity to apply for a second award. The percentage range indicated on the y-axes differ between the 2 plots; the range in common is indicated in blue. For first-time applicants and receivers of R01 grants, P⬍.001 for both comparisons (clinical MD vs nonclinical MD and clinical MD and PhD vs non-clinical MD and PhD). For first- and second-time receivers of R01 grants, P=.02 for non-clinical MD vs nonnon-clinical MD and P=.003 for clinical MD and PhD vs nonclinical MD and PhD.
cants; are recipients of funding for their first application and then reapply for a second R01 grant; are unsuccessful in their first application but later reapply for a different R01 grant; and are appli-cants who do or do not conduct clini-cal research as coded by the NIH.
We agree with others1-4,13,19-21that
physician-scientists bring unique skills, experience, motivation, and perspec-tive to biomedical research. They play an indispensable role, especially in de-signing and conducting the transla-tional and clinical research by which scientific advancements are brought into medical practice.
An often proposed interpretation of attrition for those with an MD from the R01 grant pool is that physicians have more competitive alternatives to R01 re-search careers.2,22Yet, abundant
anec-dotal evidence indicates that physician-scientists who leave research careers often do so because of insufficient in-stitutional support, a perceived lack of available mentors and role models, and discouragement.23-25These anecdotes
are consistent with our observation that even investigators with an MD who re-ceive their first R01 grant are less likely than their counterparts with a PhD to recompete the grant or apply for an-other R01 grant.
For medical schools and teaching hospitals, the challenge is to create a more attractive and supportive aca-demic culture that not only attracts and trains but also actively nurtures and sus-tains clinical and translational scien-tists. The recent report by the Associa-tion of American Medical Colleges’ Task Force II on Clinical Research24,25calls
on the leadership of academic medical centers to reaffirm translational and clinical research as a core mission. The report urges the establishment of cen-tral administrative oversight of shared
research facilities and of training grams for physician-scientists that pro-vide protected time for trainees and dedicated time for capable mentors, and that ensures the protected time and ac-cess to infrastructure neac-cessary to launch the careers and nurture ad-equately prepared clinical physician-scientists. Adoption of the report’s rec-ommendations, together with recent NIH program initiatives,7,8 would
greatly ameliorate the problems that have impeded development of the ro-bust clinical research enterprise that both unprecedented scientific oppor-tunity and rising public expectations demand.
Author Contributions: Dr Fang had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design:Dickler, Fang, Korn.
Analysis and interpretation of data:Dickler, Fang, Heinig, Johnson, Korn.
Drafting of the manuscript:Dickler, Heinig, Korn.
Critical revision of the manuscript for important in-tellectual content:Dickler, Fang, Heinig, Johnson, Korn.
Statistical analysis:Fang, Johnson.
Administrative, technical, or material support:Heinig, Korn.
Study supervision:Korn.
Financial Disclosures: None reported.
Funding/Support: Data used in this study have been made available under the National Institutes of Health Contract N01-OD-3-1015 with the Association of American Medical Colleges.
Acknowledgment: We thank Hershel Alexander, PhD, of the Association of American Medical Colleges for his collegiality and assistance in gaining access to As-sociation of American Medical Colleges data re-sources and systems used in this study, and Scott Zeger, PhD, professor and chair in biostatistics at the Johns Hopkins University School of Public Health for advice and guidance on statistical methods and permitting us to recruit his student (Ms Johnson) into this effort. The individuals listed in this acknowledgment were not compensated for their contributions.
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